1. Field of the Invention
The present invention relates generally to vehicle steering systems, and particularly to a trailer steering mechanism for towing a trailer behind a motor vehicle.
2. Description of the Related Art
The towing vehicle and trailer combination is an inherently unstable one during backing maneuvers. Even a simple trailer having a single axle with non-steerable wheels requires some skill by the driver of the towing vehicle during backing maneuvers. This is because of the articulation between the towing vehicle and trailer, which allows the trailer to turn relative to the towing vehicle. Once the trailer begins to turn, even continued straight backing by the towing vehicle will cause the trailer to turn ever more sharply, resulting in the jackknifing of the trailer and towing vehicle in short order.
While the above problem can be overcome by a skilled driver operating a single axle trailer, other trailer configurations can be impossible to back. For example, truck tractors, or other towing vehicles towing multiple articulated trailers in tandem, can only successfully back the single trailer connected directly to the towing vehicle. There is no way for the driver of the towing vehicle to steer both trailers of such a configuration while backing. Another example is the farm wagon-type trailer, having a front axle with steerable wheels and a rear axle with directionally fixed wheels. This combination cannot be backed due to the instability of the steerable front wheels of the trailer, which causes a castering action when backing.
A number of different trailer steering mechanisms have been developed over the years in attempts to solve at least some of the above-described problems.
German Patent No. 3,538,338, published on Apr. 30, 1987, describes (according to the drawings and English abstract) an electrical system incorporating servomotors to drive the trailer steering. The drawings are primarily directed to the electronic circuitry used in the system.
German Patent No. 4,216,543, published on Dec. 3, 1992, describes (according to the drawings and English abstract) a rigid linkage of two or more struts or tow bars between the towing vehicle and trailer, which angularly lock the trailer relative to the towing vehicle and prevent articulation therebetween. The trailer wheels are not actively steered, but, rather, caster to follow the turns of the towing vehicle during both forward and reverse travel. The lateral hydraulic cylinder disclosed in the drawings is not a steering actuation link or element, but is a shimmy damper, as conventionally applied to castering wheel systems.
Finally, German Patent No. 10,236,335, published on Feb. 27, 2003, indicates (according to the English title and abstract) that the subject trailer has a steerable front axle. However, no such steering mechanism is apparent in the drawings of the two-axle trailer. It appears that the trailer actually has castering front wheels, with no positive steering system being apparent.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a trailer steering mechanism solving the aforementioned problems is desired.